One hundred and forty-seven patients undergoing elective or emergency Caesarean section under general anaesthesia were allocated randomly to three groups: group 1 (n = 28) received no premedication; group 2 (n = 58) received 0.3-molar sodium citrate 15 ml (sodium citrate 1.16 g); group 3 (n = 61) received effervescent cimetidine-sodium citrate combination (cimetidine 400 mg with sodium citrate 0.9 g) after entering the operating room. Gastric pH was measured at tracheal intubation (pH1) and extubation (pH2). Mean pH1 and mean pH2 values in group 1 were, respectively, 2.25 (SD 1.35) and 2.83 (1.64). Mean pH1 and pH2 values in group 2 were, respectively, 4.38 (1.44) and 4.57 (1.51). In group 3 mean pH1 and pH2 values were, respectively, 5.07 (1.13) and 5.37 (1.30). Percentages of patients with pH1 less than or equal to 2.5 in groups 1, 2 and 3 were, respectively, 75, 13.8 and 1.6. Percentages of patients with pH2 less than or equal to 2.5 in groups 1, 2 and 3 were 50, 10.3 and 1.6, respectively.